Yes they will! If every team decides to play their preseason rosters and cut their starters. But assuming this will not happen, highly unlikely would the Niners could jump back into their glory days in one season seeing how they're still in the beginning of their rebuilding phase, but wait, beginning of the rebuilding phase, haven't they been doing that for the last... 5 years??
I'm Niners fan myself, and I think it's unlikely, but I'll root for them. Anything can happen really.